Perioperative VTE Prophylaxis

Meet the patient

A 72-year-old man is on day 7 after a hemiarthroplasty for a fractured neck of femur. At 4am he rings the bell — sudden dyspnoea, pleuritic chest pain, and he is grey and gasping. He never mobilised as much as the physiotherapist asked, and his prophylactic enoxaparin was stopped at discharge on day 5. The sats read 86 percent on room air.[1]

Hold two questions and the whole topic slots into place: can I prevent the clot that has not yet formed without causing a bleed? and can I recognise the clot that already has? That is the central tension — prevent the clot, do not cause a bleed, and catch the one that formed.[1]

One disease, one mechanism, one ladder

Venous thromboembolism (VTE) is a single disease wearing two faces — deep vein thrombosis (DVT) and its embolic complication, pulmonary embolism (PE) — because both share Virchow's triad, the same risk factors, and the same prevention strategy.[1]

In surgical patients, perioperative VTE prophylaxis is the systematic, evidence-based application of risk stratification, mechanical methods, pharmacological anticoagulation and early mobilisation. It is not optional: the ACCP 9th-edition guideline opens by calling VTE "a common cause of preventable death in surgical patients".[11] The landmark ENDORSE audit of 68 183 inpatients across 32 countries found 64.4 percent of surgical and 41.5 percent of medical inpatients at high VTE risk by ACCP criteria — yet only 58.5 percent of at-risk surgical and 39.5 percent of at-risk medical patients received ACCP-recommended prophylaxis.[1]

The shift of the last three decades is from treating established VTE to preventing it. A pulmonary embolus that never forms cannot kill a patient — four weeks of enoxaparin after cancer surgery cut VTE from 12.0 to 4.8 percent (ENOXACAN II), and prophylactic enoxaparin cut it from 14.9 to 5.5 percent in acutely ill medical patients (MEDENOX). The bedside art is the balance: prevent the clot without causing a bleed — the thread that runs through every section below.[2][14]

Two sorts of tool, four rungs of risk — the prophylaxis ladder

VTE prevention sorts itself twice — by the type of intervention, and by the patient's risk stratum. Read the two together and you have the whole ladder.[1]

Duration is the other axis examiners test. Cancer surgery extends LMWH to four weeks (ACCP Grade 1B; ENOXACAN II); hip or knee replacement needs at least 10 to 14 days, extendable up to 35 days (ACCP); the medical-prophylaxis trials ran 6 to 14 days.[2][11][12][14]

DVT sorts by anatomy, PE sorts by haemodynamics. Distal (calf) DVT sits below the popliteal vein and embolises less but can propagate; proximal DVT (popliteal, femoral, iliac) is the source of most clinically important PEs. PE is submassive when there is right ventricular strain but a stable pressure, and massive when the systolic BP drops below ninety mmHg or falls by forty mmHg for over fifteen minutes — the thrombolysis candidate.[1]

How common, who, and why the clot forms

VTE is a disease of hospitalisation. Fifty to seventy percent of all symptomatic DVT and PE events happen in patients who are, or have recently been, in hospital, and ten to thirty percent of unprotected major-surgery patients develop DVT on screening imaging.[1]

Baseline (untreated) DVT incidence without prophylaxis, by procedure: [1]

ENDORSE proved the point at scale: across 32 countries and 68 183 inpatients, 51.8 percent met ACCP high-risk criteria (64.4 percent of surgical and 41.5 percent of medical patients), yet only 58.5 percent of at-risk surgical and 39.5 percent of at-risk medical patients received ACCP-recommended prophylaxis — thromboprophylaxis is a global, cross-specialty duty, not an orthopaedic or cancer-only concern.[1]

Each risk factor below is a point on the Caprini score — learn them as the score, not as a list.[1]

• Age — risk climbs after forty, steeper after sixty, steepest over seventy-five.
• Previous VTE — the single strongest factor, roughly eight-fold.
• Active malignancy and chemotherapy — compression, tumour procoagulants and immobility converge.
• Obesity (BMI above thirty) and the metabolic syndrome.
• Pregnancy, puerperium, combined oral contraceptive pill, HRT, tamoxifen.
• Inherited thrombophilia — Factor V Leiden, prothrombin G20210A, antithrombin, protein C and S deficiency, antiphospholipid syndrome.
• Acute medical illness — heart failure (NYHA III-IV within a month), COPD exacerbation, pneumonia, sepsis, acute stroke with paralysis, inflammatory bowel disease.
• Varicose veins, central lines, nephrotic syndrome, myeloproliferative disorders.[1]

The surgical amplifier: general anaesthesia beyond forty-five minutes, pelvic or lower-limb surgery, an immobilising plaster cast, bed rest over seventy-two hours, and the surgical stress response itself.[1]

Virchow's triad — and surgery violates all three limbs at once

All VTE flows from Virchow's triad — and every surgical patient breaches all three limbs simultaneously, which is the molecular reason for the ten- to twenty-fold excess risk.[1]

Etymology for viva gold: Rudolf Virchow named the triad in 1856. The word thrombosis is Greek — thrombos means a clot, and the suffix denotes the condition of forming one. The name has outlived its coiner because the pathology it describes is unchanged.[1]

1. Stasis. General and neuraxial anaesthesia switch off the calf-muscle pump; intra-operative venodilation slows flow; pain, opioids and catheters keep the patient supine. Blood pools in the valve pockets of the deep calf veins — the classic site where a clot begins — and low shear stress down-regulates endothelial thrombomodulin, tilting toward coagulation.[1]

2. Hypercoagulability (the surgical stress response). Damaged tissue releases tissue factor, which with factor VIIa activates factor X and generates thrombin; thrombin makes fibrin, activates platelets, and feeds back to amplify factors V and VIII. Perioperatively, fibrinogen, factor VIII and von Willebrand factor rise, platelets activate, and fibrinolysis is blunted by plasminogen activator inhibitor-1. Malignancy and pregnancy layer their own procoagulants on top.[1]

3. Endothelial injury. Surgical trauma denudes the protective endothelial monolayer, exposing collagen and tissue factor; venous cannulation, orthopaedic leg manipulation and previous DVT do the same. Healthy endothelium is antithrombotic — thrombomodulin, heparan sulphate, tissue-factor pathway inhibitor, prostacyclin, nitric oxide. Injury flips the phenotype to prothrombotic.[1]

The cascade: a clot starts as a platelet-fibrin nidus in a calf-vein valve sinus, then lyses, stays put, or climbs into the popliteal, femoral and iliac veins. Proximal clot — especially iliofemoral — is the one that detaches and embolises. About half of proximal DVTs embolise; calf clots embolise less often but up to twenty percent climb proximally, which is why you never dismiss a distal clot.[1]

The silent clot — why prophylaxis beats detection

Most perioperative DVTs are clinically silent — they declare themselves only when they embolise. That silence is exactly why prophylaxis, not detection, is the goal.[1]

DVT (classic features):[1]

• Calf or thigh pain, swelling, warmth and erythema of the affected limb.
• Calf tenderness with a tense, woody feel; a calf more than three centimetres larger than the other leg is significant.
• Superficial venous dilation and visible collaterals.
• Homans' sign (calf pain on forced dorsiflexion) and Pratt sign (pain on squeezing the calf) — historical, painful, unreliable, and they can dislodge clot. Drop them from practice, keep them for the viva.[1]

Atypical presentations that bite surgical patients:[1]

• The elderly show only unexplained tachycardia, confusion, or a fall.
• The diabetic or neuropathic patient has a painless swollen leg.
• Pregnancy and postpartum — left-leg predominance from May-Thurner anatomy (the right iliac artery compressing the left iliac vein).
• Massive iliofemoral DVT as phlegmasia alba dolens (white, painful, swollen leg) progressing to phlegmasia cerulea dolens (blue, tense limb, impending venous gangrene) — a vascular emergency.[1]

Pulmonary embolism:[1]

• Sudden dyspnoea — the commonest symptom, in over eighty percent.
• Pleuritic chest pain — from pulmonary infarction, in about half.
• Haemoptysis, cough, syncope.
• Tachypnoea and tachycardia — the most sensitive bedside signs.
• Hypoxia, raised JVP, right ventricular heave, loud pulmonary component of S2.
• Massive PE — sudden cardiovascular collapse, electromechanical dissociation, cardiac arrest, sudden death.
• Atypical PE — isolated new atrial fibrillation, unexplained fever, or panic and anxiety in a postoperative patient.[1]

The mimics — a swollen leg or postoperative breathlessness is not VTE until proven

A swollen leg or postoperative dyspnoea is not VTE until proven — exclude the mimics actively.[1]

A swollen leg or postoperative dyspnoea is not VTE until proven, but several mimics must be actively distinguished: [1]

Two scores do the work — Caprini for the knife, Padua for the ward

Every adult admitted to hospital gets a documented VTE risk assessment and a parallel bleeding risk assessment — within fourteen hours of admission, and again before and after surgery. Two validated scores own the bedside.[1]

Caprini — the surgical score

The Caprini score sums weighted risk factors into a total that maps straight to a prophylaxis tier — it is the standard surgical VTE tool.[9][1]

One point each: age forty-one to sixty; minor planned surgery under forty-five minutes; BMI above twenty-five; swollen legs; varicose veins; pregnancy or postpartum; unexplained or recurrent miscarriage; oral contraceptives or HRT; sepsis within a month; serious lung disease (including pneumonia) within a month; abnormal pulmonary function (COPD); acute myocardial infarction; congestive cardiac failure within a month; bed rest; inflammatory bowel disease; medical patient at bed rest.[1]

Two points each: age sixty-one to seventy-four; arthroscopic surgery; major open surgery over forty-five minutes; laparoscopic surgery over forty-five minutes; malignancy present or past; bed rest over seventy-two hours; immobilising plaster cast; central venous line.[1]

Three points each: age seventy-five or older; personal or family history of VTE in a parent or sibling; Factor V Leiden; other congenital thrombophilia (prothrombin mutation, antithrombin or protein C or S deficiency); lupus anticoagulant, anticardiolipin or anti-beta-2-glycoprotein antibodies; raised homocysteine; heparin-induced thrombocytopenia.[1]

Five points each: stroke within a month; elective major lower-extremity arthroplasty (THR or TKR); hip, pelvis or leg fracture within a month; acute spinal cord injury or paralysis within a month; multiple trauma within a month.[1]

Risk strata and recommended action: [1]

Padua — the medical score

For non-surgical inpatients, the Padua Prediction Score replaces Caprini.[8]

• Three points each: active cancer (recurrence, metastasis, or chemo or radiotherapy within six months); previous VTE; reduced mobility (bed rest at least three days); known thrombophilia.
• Two points: recent (within a month) trauma or surgery.
• One point each: age seventy or over; heart or respiratory failure; acute myocardial infarction or ischaemic stroke within a month; acute infection or rheumatologic disorder; obesity (BMI thirty or more); ongoing hormonal treatment.[1]

Padua high-risk patients are the ones who need prophylaxis: 11.0 percent developed VTE without it versus 2.2 percent with it, and low-risk patients sat at 0.3 percent — a hazard ratio of 32 for untreated high risk.[8]

Bleeding risk — the second assessment you must not skip

A Caprini or Padua score alone is half the job — the bleeding risk sits beside it. The IMPROVE score is the alternative medical model (two or more is high risk). The bleeding flags: active gastroduodenal ulcer, bleeding within three months before admission, platelets below fifty, age over eighty-five (or seventy-five for ACCP), hepatic or renal failure, ICU admission, concurrent anticoagulant or antiplatelet therapy. When bleeding risk is high, prefer mechanical prophylaxis alone until it falls.[1]

Consultant confession: I write the Caprini and the bleeding score side by side on the drug chart before I pick the agent — it stops me defaulting to enoxaparin for everyone, and it survives handover better than a plan buried in the notes.[1]

Compression ultrasound for DVT, CTPA for PE — D-dimer only if low

Investigations are for suspected established VTE — prophylaxis itself needs no routine monitoring for LMWH. They run off clinical pre-test probability.[1]

Wells score for DVT: active cancer (+1); paralysis, paresis or plaster cast of a lower limb (+1); bedridden at least three days or major surgery within twelve weeks (+1); localised tenderness along the deep venous system (+1); entire leg swollen (+1); calf swelling at least three centimetres more than the other leg (+1); pitting oedema confined to the symptomatic leg (+1); collateral superficial non-varicose veins (+1); previously documented DVT (+1); alternative diagnosis at least as likely (minus two). Two or less is "DVT unlikely" (about five percent have DVT); three or more is "DVT likely" (about twenty to fifty percent).[1]

Wells score for PE (simplified): clinical signs or symptoms of DVT (+1); PE more likely than alternative (+1); heart rate above one hundred (+1); immobilisation at least three days or surgery within four weeks (+1); previous DVT or PE (+1); haemoptysis (+1); malignancy (+1). One or less is "PE unlikely"; two or more is "PE likely".[1]

The tests:[1]

• D-dimer — highly sensitive, poorly specific (raised in malignancy, infection, pregnancy, postoperatively, after trauma). A negative D-dimer in a low-probability patient excludes DVT or PE; a raised value mandates imaging. Predictably high after surgery, so use it sparingly on the surgical ward.
• Compression ultrasonography (venous duplex) — first-line and gold-standard for DVT. Non-compressibility of a vein under probe pressure is diagnostic; sensitivity for proximal DVT exceeds ninety-five percent, less reliable for isolated calf DVT (serial scan at one week if negative and suspicion persists).
• CT pulmonary angiography (CTPA) — first-line imaging for PE; filling defects in the pulmonary arterial tree are diagnostic, and it catches alternative diagnoses (pneumonia, dissection). The test of choice when the patient is stable.
• Ventilation-perfusion (V or Q) scan — when CTPA is contraindicated (severe renal failure, contrast allergy, pregnancy); definitive only when normal or high-probability.
• Echocardiography, ECG, troponin or BNP — in suspected submassive or massive PE show right ventricular strain (right-heart dilation, McConnell sign, raised troponin or BNP, right axis deviation, S1Q3T3 — a non-specific, late sign).
• Lower-limb venous ultrasound — in suspected PE if CTPA is unavailable, as a proximal DVT confirms the need to treat.[1]

Massive PE — oxygen, heparin, and lysis if the pressure drops

Established massive PE is a perioperative emergency, and the resuscitation bundle is time-critical.[1]

1. Call for help — arrest team, ICU, anaesthetics, haematology.
2. Airway and breathing — high-flow oxygen; escalate ventilatory support for respiratory failure.
3. Circulation — large-bore access and cautious haemodynamic support; over-resuscitation can worsen right-heart failure.
4. Anticoagulation and thrombolysis — the CHEST guideline suggests thrombolytic therapy for pulmonary embolism with hypotension (Grade 2B) and favours systemic over catheter-directed thrombolysis (Grade 2C).
5. Escalation — surgical embolectomy or catheter-directed options when thrombolysis is contraindicated or fails; CHEST recommends against an inferior vena cava filter in patients treated with anticoagulants (Grade 1B).[13]

For the unstable postoperative patient with suspected PE, the choice between empirical thrombolysis and CTPA weighs the freshness of the surgical wound against the immediacy of death. Involve the surgical team and the senior clinician immediately.[1]

The ladder — mobilise, compress, anticoagulate

The definitive strategy is risk-stratified prophylaxis, applied to every patient and reviewed daily.[1]

Pharmacological prophylaxis dosing

The twelve-hour rule — neuraxial needles and LMWH

The classic trap: timing a neuraxial needle wrong against LMWH causes a spinal haematoma — a devastating, largely irreversible paralysis. The numbers are non-negotiable. Allow at least twelve hours after a prophylactic LMWH dose before spinal or epidural needle insertion, at least twenty-four hours after a therapeutic dose, and at least four hours after catheter removal before the next dose. If you cannot meet these windows, defer the block or defer the dose.[1]

Mechanical prophylaxis

Match the rung to the score

The ladder maps straight onto the Caprini tier — climb it as the score rises, and add a rung when bleeding risk is low.[1]

1. Very low (Caprini 0) — early, frequent ambulation. No routine pharmacological or mechanical prophylaxis.
2. Low (Caprini 1 to 2) — mechanical; IPC over stockings alone.
3. Moderate (Caprini 3 to 4) — LMWH, low-dose UFH or IPC; add the second if bleeding risk is low.
4. High or very high (Caprini at least 5) — combined pharmacological plus mechanical; the additive benefit is well established.
5. Start timing — LMWH or fondaparinux within twelve hours of surgery (commonly six to twelve hours post-op, or evening before for elective surgery); IPC before induction and until full mobility.[1]

When prophylaxis fails — treating established VTE

• Acute anticoagulation — therapeutic LMWH or UFH: the landmark home-treatment trial used enoxaparin 1 mg per kg subcutaneously twice daily against in-hospital unfractionated heparin, with warfarin from day two.[16]
• Long-term agent — for VTE without cancer, CHEST suggests a DOAC (dabigatran, rivaroxaban, apixaban or edoxaban) over VKA; for VTE with cancer, LMWH over the alternatives.[13]
• Duration — CHEST distinguishes stopping anticoagulation at 3 months from extended therapy; a first provoked event generally stops at 3 months.[13]
• Thrombolysis — reserved for PE with hypotension, systemic over catheter-directed.[13]
• Compression stockings — CHEST suggests NOT using them routinely to prevent post-thrombotic syndrome after DVT (Grade 2B).[13]

The other classic trap: do not confuse the doses. Prophylactic enoxaparin is 40 mg SC once daily — the dose trialled in cancer surgery and in acutely ill medical patients (where 20 mg once daily failed); therapeutic enoxaparin is 1 mg per kg twice daily, the home-treatment dose for proximal DVT. Writing 1 mg per kg twice daily as prophylaxis fully anticoagulates a postoperative patient and invites a wound haematoma.[2][14][16]

The high-risk operations — orthopaedics, cancer, trauma, neurosurgery

Major orthopaedic surgery — the longest durations. ACCP recommends at least 10 to 14 days of prophylaxis after hip or knee replacement and suggests extending up to 35 days, preferring LMWH and adding an intermittent pneumatic compression device during the hospital stay.[12] The hip-replacement trials ran apixaban 2.5 mg twice daily (started 12 to 24 hours after wound closure) against enoxaparin 40 mg once daily for 35 days, and dabigatran 220 mg once daily (half dose 1 to 4 hours post-op) for 28 to 35 days — both matched enoxaparin, and apixaban was significantly better (1.4 versus 3.9 percent).[3][4]

Cancer surgery (ENOXACAN II) extends enoxaparin to twenty-eight days after curative abdominal or pelvic cancer surgery — it cut venographic DVT from twenty-one to twelve percent without excess bleeding.[2] Hospitalised medical patients with active cancer also warrant prophylaxis throughout admission.[1]

Neurosurgery is the classic dilemma — high VTE risk, high bleeding consequence. Start mechanical prophylaxis (IPC, with or without TEDS) intra-operatively; defer LMWH for forty-eight to seventy-two hours until haemostasis is secure, then add it. Post-haemorrhagic traumatic brain injury follows the same delayed-start strategy.[1]

Major trauma and spinal cord injury are among the highest-risk groups. Apply mechanical prophylaxis immediately and start LMWH once major bleeding is excluded (typically thirty-six to seventy-two hours). IVC filters are reserved for confirmed proximal DVT when anticoagulation is absolutely contraindicated.[1]

Major general, abdominal and urological surgery: apply the ACCP tiers — moderate risk (about 3 percent) gets LMWH, low-dose UFH or IPC; high risk (about 6 percent) gets LMWH or low-dose UFH with a mechanical measure added; cancer surgery extends LMWH to four weeks; when bleeding risk dominates, use IPC until it falls.[11]

Medical patients (medical VTE prophylaxis): acutely ill medical inpatients benefit from prophylaxis — MEDENOX (enoxaparin 40 mg once daily for 6 to 14 days: VTE 5.5 versus 14.9 percent), PREVENT (dalteparin 5000 IU once daily for 14 days: 2.77 versus 4.96 percent) and ARTEMIS (fondaparinux 2.5 mg once daily for 6 to 14 days: 5.6 versus 10.5 percent).[14][6][7] ENDORSE still found only 39.5 percent of at-risk medical inpatients receiving ACCP-recommended prophylaxis.[1]

Vascular surgery is tailored: high-risk aortic or major reconstructions get LMWH plus IPC; lower-limb bypass balances graft patency against bleeding.[1]

Complications — thrombosis, bleeding, and the prothrombotic paradox

Inadequate prophylaxis kills and disables through thrombosis:[1]

• Fatal PE — the catastrophic, largely preventable outcome.
• Post-thrombotic syndrome — chronic venous hypertension after DVT from valve destruction and persistent obstruction; affects twenty to fifty percent, with leg heaviness, swelling, pain, hyperpigmentation, lipodermatosclerosis and venous ulcers. Reduced by early adequate anticoagulation.
• Chronic thromboembolic pulmonary hypertension (CTEPH) — organised residual PE remodels pulmonary arteries; presents months to years later with exertional dyspnoea and right-heart failure; pulmonary endarterectomy is the treatment.
• Recurrent VTE — up to thirty percent at ten years after a first event.[1]

Over-prophylaxis bleeds:[1]

• Wound haematoma — the commonest, and a particular concern after neurosurgery and urology.
• Gastrointestinal, retroperitoneal and intracranial bleeding.
• The bleeding-versus-thrombosis balance is the central clinical judgement — there is no risk-free option.[1]

HIT — the prothrombotic paradox

The trap juniors miss: heparin-induced thrombocytopenia is a PROthrombotic complication, not a bleeding one. The ASH 2018 guideline recommends the 4Ts score (Thrombocytopenia, Timing, Thrombosis, oTher cause) over gestalt for estimating pretest probability, advises against laboratory testing and empiric treatment when the 4Ts probability is low, and treats acute HIT with a non-heparin anticoagulant — argatroban, bivalirudin, danaparoid, fondaparinux or a direct oral anticoagulant. When HIT is likely, discontinue all heparin exposure — LMWH and line flushes included — because the syndrome thromboses as much as it bleeds.[10]

The pitfalls that lose marks and patients:[1]

• Omitting the risk assessment — ENDORSE: only 58.5 percent of at-risk surgical inpatients received ACCP-recommended prophylaxis.[1]
• Under-treating by stratum — moderate risk still needs LMWH, low-dose UFH or IPC; high risk needs a drug plus a mechanical measure.[11]
• Stopping too early after cancer surgery — ACCP recommends four weeks of LMWH, Grade 1B.[11]
• Ignoring bleeding risk — when bleeding risk is high, ACCP suggests mechanical prophylaxis, preferably IPC, until it falls.[11]
• Confusing prophylactic and therapeutic LMWH — 40 mg once daily is prophylactic; 1 mg per kg twice daily is therapeutic.[14][16]
• Reaching for an IVC filter as primary prevention — suggested against in all risk groups.[11]

Prognosis and disposition — when to stop, when to continue

With risk-stratified prophylaxis, VTE events fall by fifty to seventy percent and fatal PE becomes rare. After a confirmed DVT or PE, anticoagulation runs at least three months (provoked) to lifelong (unprovoked, recurrent, cancer-associated).[1]

Disposition: continue pharmacological prophylaxis until the patient is fully ambulating and acute illness has resolved (medical), or for twenty-eight days after major orthopaedic or cancer surgery. Patients discharged on DOACs or LMWH need education on injection technique, bleeding precautions and warning signs (dyspnoea, chest pain, leg swelling, bleeding). Mechanical prophylaxis continues at home if mobility is still impaired.[1]

Mortality of untreated massive PE is about thirty percent; with prompt recognition, anticoagulation and thrombolysis it falls below ten percent. Recurrence risk is highest in the first month after an event.[1]

Special populations — pregnancy, renal failure, the elderly, the already-anticoagulated

Pregnancy and the postpartum period: pregnancy is hypercoagulable and pro-stasis, and VTE is a leading cause of maternal death. LMWH is the agent of choice throughout pregnancy and lactation — it does not cross the placenta. Warfarin is teratogenic (first trimester) and causes fetal bleeding (third trimester); DOACs are contraindicated in pregnancy and breastfeeding. Emergency caesarean and additional risk factors (previous VTE, thrombophilia, obesity) warrant LMWH for at least six weeks postpartum. Neuraxial labour analgesia obeys the same LMWH-timing rules as surgical anaesthesia.[1]

The elderly: higher baseline VTE risk, more comorbidity, more polypharmacy, higher bleeding risk — reassess daily, favour IPC plus cautious pharmacological dosing, and avoid DOACs in the severe renal impairment common in this group.[1]

The already-anticoagulated patient: stop the DOAC two to five days pre-op (drug- and renal-dependent), stop warfarin five days pre-op, bridge with therapeutic LMWH (last dose twenty-four hours pre-op) if thromboembolic risk is high (mechanical mitral valve, recent VTE, AF with prior stroke), and resume post-operatively when haemostasis is secure.[1]

The trials that set the durations

Guidelines:[11]

• ACCP 9th edition (2012), nonorthopaedic surgery — risk-stratified tiers from very low (under 0.5 percent) to high (about 6 percent); LMWH or low-dose UFH for moderate and high risk with mechanical added for high; four-week extended LMWH after abdominal or pelvic cancer surgery (Grade 1B); no IVC filters or surveillance ultrasound for primary prevention.[11]
• ACCP 9th edition (2012), orthopaedic surgery — LMWH preferred among the recommended agents (fondaparinux, dabigatran, apixaban, rivaroxaban, low-dose UFH, adjusted-dose VKA, aspirin, IPCD) for at least 10 to 14 days; extension up to 35 days suggested; apixaban or dabigatran for patients who decline injections.[12]
• CHEST 2016 VTE-treatment guideline — DOAC-first long-term therapy for VTE without cancer, LMWH-first with cancer; the 3-month versus extended-therapy decision; thrombolysis for PE with hypotension.[13]
• ASH 2018 HIT guideline — 4Ts score for pretest probability; argatroban, bivalirudin, danaparoid, fondaparinux or a DOAC for acute HIT.[10]

Controversies: the net benefit of extended DOAC prophylaxis in medical patients (MAGELLAN showed efficacy at the cost of bleeding; MARINER was neutral overall); whether asymptomatic distal DVTs on surveillance ultrasound warrant treatment; the optimal orthopaedic agent (DOACs are convenient but costlier and lack universal reversal — idarucizumab reverses dabigatran, andexanet reverses apixaban and rivaroxaban); and the role of DOACs immediately post-neurosurgery, still limited by bleeding.[5]

The mantra

The mantra: Every surgical patient gets a Caprini and a bleeding score — then you match the ladder.[1]

The numbers that win the stem: prophylactic enoxaparin 40 mg SC once daily, therapeutic enoxaparin 1 mg per kg twice daily, fondaparinux 2.5 mg SC once daily, apixaban 2.5 mg twice daily, dabigatran 220 mg once daily, rivaroxaban 10 mg once daily, dalteparin 5000 IU once daily — with four weeks after cancer surgery and up to 35 days after hip or knee replacement.[2][3][4][5][6][7][12][14][16]

Exam pearls

• VTE is a common cause of preventable death in surgical patients — the ACCP 9th-edition opening line.[11]
• Caprini for surgical, Padua for medical risk assessment; Padua-flagged high-risk patients run 11.0 percent VTE without prophylaxis.[8][9]
• ACCP tiers: very low — ambulation; low — IPC; moderate — LMWH, low-dose UFH or IPC; high — drug plus mechanical.[11]
• LMWH (enoxaparin 40 mg SC once daily) is standard prophylaxis; therapeutic enoxaparin is 1 mg per kg twice daily — never confuse the two.[2][14][16]
• Fondaparinux 2.5 mg SC once daily — synthetic pentasaccharide; ACCP-accepted in orthopaedic surgery.[7][12]
• DOAC prophylaxis: apixaban 2.5 mg twice daily and dabigatran 220 mg once daily after hip replacement (28 to 35 days); rivaroxaban 10 mg once daily in acutely ill medical patients.[3][4][5]
• Extended prophylaxis: four weeks of LMWH after cancer surgery (Grade 1B); up to 35 days after hip or knee replacement.[2][11][12]
• High risk gets both modalities — add elastic stockings or IPC to pharmacological prophylaxis.[11]
• HIT: use the 4Ts score; treat acute HIT with argatroban, bivalirudin, danaparoid, fondaparinux or a DOAC.[10]
• Massive PE with hypotension: thrombolytic therapy — systemic over catheter-directed (CHEST).[13]
• Post-thrombotic syndrome: CHEST suggests against routine compression stockings to prevent it after DVT.[13]
• Investigations: ACCP recommends against screening duplex ultrasound before discharge — test only suspected VTE.[11]
• IVC filter: suggested against for primary prevention, and against in anticoagulated VTE patients — never a substitute for prophylaxis.[11][13]
• ENDORSE: 51.8 percent of 68 183 inpatients at risk; only 58.5 percent of at-risk surgical patients prophylaxed.[1]

Exam application bank (NEET-PG and INICET)

One-line answer

Venous thromboembolism (VTE) = deep vein thrombosis (DVT) + pulmonary embolism (PE) — a common cause of preventable death in surgical patients (ACCP 9th ed). ENDORSE found 64.4 percent of surgical inpatients at high risk with only 58.5 percent prophylaxed. Prevention is risk-stratified: early ambulation for very low risk, IPC for low risk, LMWH or low-dose UFH for moderate and high risk (mechanical added for high risk). Trial-proven doses: enoxaparin 40 mg SC once daily, dalteparin 5000 IU once daily, fondaparinux 2.5 mg once daily, apixaban 2.5 mg twice daily, dabigatran 220 mg once daily, rivaroxaban 10 mg once daily. Extend four weeks after cancer surgery and up to 35 days after hip or knee replacement. Massive PE with hypotension: systemic thrombolytic therapy.[1][2][3][4][5][6][7][11][12][13][14]

Worked stems (answer without another resource)

Stem 1 — Classic presentation. Map symptoms to mechanism; name the first investigation and first treatment step with dose and route if drug therapy is standard.[1]

Stem 2 — Unstable or complicated. List the red flags that force immediate resuscitation, theatre, ICU, antidote or reperfusion — and what you do in the first fifteen minutes.[1]

Stem 3 — Atypical group. Elderly, pregnancy, child or immunocompromised: how presentation and thresholds change.[1]

Stem 4 — Differential trap. Name the three closest mimics and one discriminator for each.[1]

Stem 5 — Disposition. Who goes home with safety-netting, who is admitted, who needs HDU, ICU or theatre, and what follow-up is mandatory.[1]

Rapid viva checklist

1. Definition and classification
2. Pathophysiology chain
3. Bedside signs and criteria
4. Score with exact components (if any)
5. Emergency bundle
6. Definitive therapy with doses
7. Complications of disease and of treatment
8. Special populations
9. Guideline or trial name if classic
10. Three exam traps.[1]

Coverage self-check

If you cannot answer any stem above from this page alone, re-read the matching section — the page is intended to be self-sufficient for final-prof and NEET-PG or INICET questions on Perioperative VTE Prophylaxis.[1]

Ward-round test — two stems, thirty seconds each